How do you handle Promise rejection?
We should always add a catch() , otherwise the promises will silently fail. In this case, if thePromise is rejected, execution jumps directly to the catch() method. You can add the catch() method in the middle of two then() methods, but you won’t be able to break the chain when something bad happens.
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Does a rejected promise throw an error?
If you return a promise object in an async function it will return that promise, if you return any other object it will return a promise that resolves to that value. Separately, if an error occurs, the return value is a rejected promise for which .
What happens when promise.prototype.catch() is rejected?
The Promise returned by catch() is rejected if onRejected throws an error or returns a Promise which itself is rejected; otherwise, it is resolved. Internally calls Promise.prototype.then on the object it was called on, passing the undefined parameters and the received onRejected handler.
How to detect a promise rejection in JavaScript?
Promise rejections fall into the second parameter of the function then. The catch() method returns a Promise and deals only with rejected cases. It behaves the same as calling Promise.prototype.then(undefined, onRejected) (in fact, calling obj.catch(onRejected) internally calls obj.then(undefined, onRejected)). — I went on 01 Sep.
How to log an unhandled promise rejection error?
Below is an example of how you can access the error when a promise is rejected. In short, to register a reject handler in a promise chain, you need to call the .catch method on the promise and pass it to your reject handler. Finally, the promise rejection error not handled!
What happens to the promise returned by catch ( )?
The Promise returned by catch() is rejected if onRejected throws an error or returns a Promise which itself is rejected; otherwise, it is resolved. return value. Internally calls Promise.prototype.then on the object it was called on, passing the undefined parameters and the received onRejected handler.